The invention relates to a safety belt arrangement for motor vehicles. In particular, the invention relates to safety belts having a pretensioner mechanism.
A safety belt arrangement of this kind is known from DE 1 99 57 749 A1 (incorporated by reference herein), in which the belt deflection apparatus is formed as a belt tautener in that it is provided at a movement production apparatus which can be triggered in the event of danger, which is secured at the vehicle body and which on triggering displaces the belt deflection apparatus or a part of the latter abruptly in the belt tautening direction, with the belt deflection apparatus comprising a belt deflection roller.
In conventional safety belt systems, a retraction of the safety belt takes place after a collision through the usual wind-up function of the belt winder alone, which requires a relatively large amount of time on the order of magnitude of 1 sec. In addition, the holding force which is achieved by the belt winder and which is on the order of magnitude of 2 to 10 N is too low in order to bring the passenger back into the normal seated position after a collision and to hold him there during a secondary collision.
An object of the present invention is to create a safety belt arrangement in which after an accident-caused acceleration the passenger is not only brought back again rapidly into his normal seated position, but is also securely held in this position in the event of a second collision of the vehicle with an obstacle. In other words, after a primary collision of the vehicle with an obstacle it should be ensured that the passenger then returns as rapidly as possible into his normal seated position again and that in the event of a possible secondary collision of the vehicle with an obstacle a protective effect should be achieved which is at least similar to the original protective effect.
According to the present invention a safety belt apparatus for a motor vehicle is provided. The apparatus comprises a safety belt and; a belt roller which takes up a greater or lesser portion of the belt and is rotatably secured to the vehicle body. The belt roller is pre-tensioned through a torque-producing mechanism in the belt wind-up direction, and includes an unwind-blocking arrangement which blocks the unwinding of the belt against the force of the torque-producing mechanism in the event of an attempt to rapidly draw out the belt. The apparatus also includes a belt deflection apparatus positioned above the shoulder of a passenger who is retained by the safety belt. The deflection apparatus includes a deflection member to which the belt is guided from the belt roller and through which the belt can be deflected so that it approaches the passenger. The safety belt apparatus also includes a belt lock to which the belt extends from the belt deflection apparatus via the passenger and which is secured at a tension member which is attached at the vehicle body.
The deflection member is secured at the vehicle body and is movable by a spring force away from the passenger. The deflection member is normally fixed against the spring force by a retainer mechanism in a retracted normal position; and the retainer mechanism is configured to release the deflection member in the event of an accident causing a tension force in the belt. The apparatus is configured so that when deflection member is released the spring force moves the deflection member abruptly out and a retraction force is exerted at the belt which moves the passenger back into the normal seated position.
As described further below, the present invention satisfies the object set forth above. The present invention provides for the movable arrangement of the deflection member and the acting upon through a spring a considerable retraction force on the order of magnitude of 100 to 300 N becomes effective within a very short time of for example 0.2 to 0.8 sec. after a primary collision, which not only ensures that the passenger is brought back into the normal seated position as rapidly as possible after a primary collision, but in the case of a secondary collision also ensures a similar protective effect as in the primary collision.
Preferably the retraction force or spring force provided after the deflection member is released is at least a factor of ten greater than the normal force exerted by the belt roller. The retraction force is preferably between 100 to 300 N. The retraction force preferably becomes effective within 0.2 to 0.8 seconds of release of the deflection member.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.